Pritha Chatterjee, Sumat C. Jain, Chattulaal Maity, M.M. Ghangrekar, A. Real, C. A. Aragon, I. Martin and J.J. Salas Presented by: Prof. M.M. Ghangrekar Department of Civil Engineering IIT Kharagpur, India www.ghangrekar.com
Background Traditionally, wastewater treatment has focused on pollution abatement, public health protection and environmental protection by removing biodegradable material, nutrients and pathogens. Wastewater recycling, reuse and resource recovery can be a very good approach to conserve water particularly in areas of water shortage. Conventional sewage treatment processes involve high capital, maintenance and operational cost, huge energy requirements, which makes them unsuitable for use in developing countries. Energy efficient low-cost waste treatment systems are the best choice for such countries. Anaerobic treatment systems excel in such respect. UASB reactors are the most widely used high rate anaerobic sewage treatment process and several full scale reactors are in operation world-wide. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized Conference on 2 Resources-Oriented Sanitation
Need of Study Most of the successful applications of UASB reactors are to treat high strength industrial wastewaters. Sato et al. (2006) evaluated the treatment efficiency of the sixteen UASB reactor based sewage treatment plants on the Yamuna river basin in India and observed that none of the plants met the discharge standards. In order to improve the effluent quality up to disposal standards, polishing ponds with short retention time were used to treat the UASB effluent. Unfortunately, effluent quality did not follow the desired standard limits even after the polishing ponds. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 3 Conference on Resources-Oriented Sanitation
Objectives Possibility of producing reusable quality treated wastewater by a combined UASB-HRAP system is explored. While UASB will help in organic matter removal, HRAP will abate nutrients and pathogens. The treated wastewater after UASB-HRAP can be used for landscape irrigation (parks, playgrounds, and school yards), fire protection, construction, ornamental fountains, recreational impoundments; in- building uses (toilet flushing) etc. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 4 Conference on Resources-Oriented Sanitation
UASB-HRAP The UASB reactor was having a height of 5.3 m and diameter of 5.6 m, which is followed by a 15.8 m long and 7.9 m wide HRAP. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 5 Conference on Resources-Oriented Sanitation
General Performance of UASB reactor 6000 Reactor height (m) a The UASB reactor was operated for a 5000 total of 250 days. 4000 3000 COD removal efficiency kept on 2000 increasing with operation time, with a 1000 maximum soluble COD removal of 73 ± 0 6% and maximum total COD removal of 0 100 200 300 66 ± 10%, in the month of June. COD (mg/L) Total COD Soluble COD Average effluent COD throughout the entire range of operation was 75 ± 15 6000 Height of the Reactor (m) b mg/L. 5000 Average gas production rate was 0.39 ± 4000 0.10 m 3 /kg COD removed. 3000 2000 Methane content in the biogas was 68%. 1000 Average TSS and VSS in the effluent of 0 the UASB reactor was 31 ± 17 mg/L and 6.8 6.9 7 7.1 7.2 7.3 7.4 20 ± 10 mg/L, respectively. pH 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 6 Conference on Resources-Oriented Sanitation
Monthly average of COD removal in the UASB reactor Month COD COD Total Soluble Soluble Soluble inlet outlet COD COD COD COD (mg/L) (mg/L) removal inlet outlet removal (%) (mg/L) (mg/L) (%) Nov 167 ± 30 123 ± 30 27 ± 12 110 ± 12 77 ± 12 30 ± 8 Dec 162 ± 30 79 ± 41 49 ± 26 94 ± 21 35 ± 7 63 ± 7 Jan 193 ± 26 98 ± 19 49 ± 9 95 ± 3 39 ± 1 59 ± 1 Feb 187 ± 61 76 ± 17 56 ± 16 78 ± 23 33 ± 13 57 ± 9 Mar 250 ± 61 100 ± 18 58 ± 12 101 ± 21 38 ± 7 63 ± 10 April 195 ± 49 71 ± 11 61 ± 11 83 ± 19 23 ± 2 70 ± 8 May 215 ± 44 78 ± 31 63 ± 14 91 ± 29 23 ± 3 72 ± 7 June 232 ± 60 75 ± 15 66 ± 10 95 ± 23 25 ± 3 73 ± 6 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 7 Conference on Resources-Oriented Sanitation
Biomass Granulation Good granular sludge (percentage of granules more than 50%, w/w) can be developed in UASB reactor if BGI is maintained in the range of 240 to 560. 30 When the BGI was calculated initially with % Biomass volume 25 inoculum sludge concentration of 8 g/L, BGI was 185; however, with continued operation and 20 increase in sludge concentration within the 15 reactor the BGI value increased to an average of 10 280 and a maximum of 380, indicating a 50 – 60% 5 possibility of granulation. 0 63.47% of the sludge inside the UASB reactor 3.45 1.7 1 0.78 0.52 0.4 0.3 0.2 0.1 Particle diameter (mm) after 200 days of operation was granular sludge. Sludge after 200 days Innoculum Such percentage of granulation has not been reported while treating sewage in full scale UASB reactor earlier. SVI 5 and SVI 30 of the sludge was 31 mL/g and 28 mL/g, respectively, after 200 days of operation of the pilot reactor. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 8 Conference on Resources-Oriented Sanitation
Biomass Characterization The average VSS/SS ratio in the sludge was 0.56 and it was above 0.6 for the winter months. Lower biogas production rate was observed 12 8 in the winter months from the reactor. mg/g VSS 6 8 PN/PS 4 4 2 Sludge collected had an integrity coefficient 0 0 Settled sludge Innoculum sludge Floating sludge Settled sludge Innoculum sludge Floating sludge Settled sludge Innoculum sludge Floating sludge of 3.74%. Integrity coefficient should be less than 20% for good strength sludge. Total EPS content of the sludge collected from the bottom of the UASB reactor was Slime EPS LB EPS TB EPS 12.94 mg/g VSS. PN PS PN/PS The ratio of proteins and carbohydrates in sludge is used to determine its strength, stability and settling ability, with a higher ratio indicating low strength granules with bad settling properties and poor stability 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 9 Conference on Resources-Oriented Sanitation
Performance of HRAP Start-up of the algal pond comprised of two steps based on the ammonium removal performance: lag phase (1 – 50 days) and propagation phase (still continuing). During this lag period a reduction of ammonium was observed, but only after one month of operation, before which an increase of ammonium ion was detected due to organic hindrance or self-degradation of nutrients in wastewater thus making it unavailable to species. Ammonia removal increased to 85.1 ± 2.4%. With influent ammonia nitrogen concentrations of 20 ± 3 mg/L the average effluent ammonia nitrogen concentration was 3 ± 1 mg/L. Stable phosphate removal of 91 ± 1% observed. A final effluent total COD of around 50 ± 6 mg/L could be obtained after treatment with HRAP. There was a 4 log scale pathogen removal after treatment with HRAP with MPN of the final effluent being less than 1000/100 ml. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 10 Conference on Resources-Oriented Sanitation
Performance of HRAP 100 a 80 60 40 20 0 0 50 100 -20 Days 40 b Biomass (mg/L) TN removal (%) 30 20 10 0 0 50 100 Days Chlorophyll (mg/L) Protein (mg/L) Carbohydrate (mg/L) Lipid (mg/L) 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 11 Conference on Resources-Oriented Sanitation
Monthly average of performance data of HRAP Month BOD COD TN Outlet TP Outlet MPN outlet outlet (mg/L) Outlet (mg/L) (mg/L) 68 8 0.2 15000 Mar 26 54 5 0.5 970 April 28 77 7 0.7 920 May 27 70 7 0.1 1000 June 21 45 5 0.4 1000 July 24
Summary of Results UASB reactor successfully gave more than 70% COD removal with biomass granulation. Approximate height of sludge bed is less than 1 m at present. Further improvement in organic matter removal efficiency is expected with higher depth of sludge bed. Utilization of nutrients present in the treated sewage for the growth of microalgal species will not only control eutrophication but will also help in sustainable energy development. The findings of this study suggest that sewage can be directly used for mass cultivation of microalgae without requiring additional nutrient supplements. The effluent of the algal pond was directly reused for horticulture, landscaping and aesthetic enhancement. 23-Sep-16 13th IWA Specialized Conference on Small Water and Wastewater Systems & 5th IWA Specialized 13 Conference on Resources-Oriented Sanitation
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